Efforts are made to keep certain equipment such as sophisticated military weapons out of the hands of unauthorized users, including terrorists and military adversaries. Nevertheless, these weapons and equipment sometimes do come to be in hostile control. This may occur through theft, or through unauthorized sale. Alternatively, weapons or equipment may be sold to a foreign nation at a time when the nation is considered to be an ally, but that nation may subsequently come to be considered an adversary, for example due to a coup or some other internal political shift. Still another consideration is that it is sometimes difficult to determine who will actually be the true and ultimate recipient of weapons or equipment that are involved in a particular sale.
The fact that equipment or a weapon is present in hostile hands is a problem, not only when it is known that the particular weapon or item of equipment is in hostile hands, but also when it not yet known that the equipment or weapon has passed into hostile hands. Traditional attempts to avoid this type of problem have included strict export restrictions regarding which weapons and equipment can be exported or sold, and to whom. While these export restrictions have been helpful to some degree, they have not been satisfactory in all respects.